An equalizer is a device that alters tone color by adjusting the gain of a musical range and is used to change the atmosphere of music or compensate for sound quality. For example, the equalizer increases the gain of low frequency in order to boost low tone, and increases the gain of middle frequency in order to boost human voice. When high tone is unpleasant to the ear, the gain of high frequency is decreased.
The equalizer can also be used in a mobile communication device, generally, in order to compensate for telephone speech quality. A number of mobile communication devices adjust the tone color of received sound using an equalizer function. More specifically, the mobile communication devices are delivered in a state that the tone color of received sound is uniformly set by providers or according to the GCF standard, so that telephone speech quality can be optimized for network status.
While this approach can improve telephone speech quality, there is no user interface that allows the user to newly set the gain of received sound according to frequency using the equalizer. The problem is that it is impossible to enable the proper function of the equalizer for adjusting tone color in that the user cannot change the tone color of received sound even if he/she dislikes it.
In the case of automatic roaming service that extends the connectivity of a mobile communication device in a foreign network that is different from the domestic network where the mobile communication device was registered, the equalizer cannot optimize the tone color of received sound in the foreign network since the setting of the tone color is fixed to domestic network environments.
For example, Chinese prefer to high tone and large sound, Europeans prefer to powerful middle-low tone and clear tone color, and Americans prefer to powerful middle-low tone and smooth tone color. Therefore, in the case of using the roaming service in a foreign country, it is necessary to modify the tone color of received sound according to the network and language characteristics of the corresponding country. However, a mobile communication device of the prior art does not support such a function.